The embodiments described herein relate generally to electrical machines, and more particularly, to electrical machines including an integrated fan for use in cooling the control electronics and the stator assembly of the electrical machine.
In some known high efficiency furnaces, standard chimney air-draw effects are not sufficient to assure the required air flow through the furnace heat exchangers, and therefore, some known high efficiency furnaces utilize draft inducers to provide sufficient air flow through the heat exchangers of the furnace.
In such known draft inducers, it is common to provide a draft inducer including a blower housing and a blower wheel that is driven by an electric motor mounted to the housing. The electric motor includes a shaft providing a driving connection with the blower wheel within the draft inducer housing. Such known furnaces use such draft inducer blowers to draw the combustion air through the heat exchanger and force it up the chimney. Such known electric motors are exposed to ambient air temperatures in the range of 150 to 175 degrees Fahrenheit. Furthermore, the rotor shaft of the electric motor extends into the blower housing and is exposed to air temperatures in the range of 400 to 450 degrees Fahrenheit. Thus, such known draft inducers are typically manufactured from metal.
In some known draft inducers, the electric motor is mounted directly to the blower housing and the bearing nearest the blower housing is exposed to an excessive amount of heat both radiated from the surface of the blower housing and conducted through the shaft of the motor. Some known draft inducers space the electric motor away from the blower housing and add a fan to the motor shaft between the motor and blower. The fan blade introduces air movement axially through the electric motor and across the surface of the housing. Such known systems are only marginal in controlling shaft end bearing temperatures because air is drawn along the outer portion of the stator assembly where it cannot effectively cool the motor. The hot air is thrown radially from the fan blade, but the hot air recirculates around the motor and reduces the effectiveness of the system.